Method and system for positive evacuation of solar collector

ABSTRACT

A method and system for positive evacuation of water from a solar collector using a bypass line which diverts a portion of water from the feed line of the solar collector to an inlet of a water pump. When the solar water heating circuit is turned off, suction created by the filtration pump rapidly evacuates all or substantially all water present in the solar collector. The system should include a water level switch on the feed line to the solar collector, a drain valve that allows pool water to evacuate from the solar collector and associated piping when water is present, a control mechanism that relays information from the water level switch to the drain valve, a small drain line that connects the solar pool heater feed and return lines to a water pump inlet, and a check valve to prevent by-pass.

This invention relates to a method and system for positive evacuation ofwater from a solar collector. More particularly, the invention relatesto a method to ensure positive water removal from the solar collectorusing a bypass line which diverts a portion of water from the feed lineof the solar collector to an inlet of a water pump.

BACKGROUND OF THE INVENTION

Solar pool heating collectors are gaining wide acceptance in bothresidential and commercial applications due to their ability to heatpool water to a comfortable temperature and their low installation andoperational costs. These solar heating collectors typically comprise anintake and exhaust manifold connected to one or more solar collectorpanels which transfer solar energy to water contained in conduits in thepanels. U.S. Pat. Nos. 6,787,116 and 7,112,297, the disclosures of whichare each incorporated by reference herein in their entirety, disclose animproved solar collector.

Solar pool heating systems incorporated into a commercial swimming poolmust accommodate continuous pumping. More particularly, public healthcodes require filtration pumps of commercial pools to operatecontinuously so as to filter the pool's water volume a minimum of 4times in a 24 hour period. Of course, residential pool pumps may also beoperated continuously.

The continuous filtration/flow requirement of commercial pools is atodds with a solar heating apparatus, whose collector cannot absorb solarradiation at night. Instead, the solar collector can act as a radiatorat night, and reduce the temperature of water flowing through it.Moreover, freezing temperatures can damage the solar collector and itsassociated plumbing.

When a solar pool heater is operating, water flow from the filtrationpump is diverted to the solar heating collectors by the use of athree-way valve, a three way valve with a booster pump or a two-wayvalve and booster pump. The solar heating operation continues untileither the swimming pool water reaches the desired temperature or usablesolar energy required for heating the pool is no longer available.

Solar heating is typically terminated by closing the water flow path tothe solar collectors and turning off the solar booster pump, if present.However, terminating the solar heating operation can trap and immobilizepool water in the solar collectors and in associated feed and returnpiping. Unless this stationary pool water is removed, the solar heatingcollectors and associated piping can be damaged by freezingtemperatures. Also, stationary water in the solar heating collector canrise to temperatures up to or exceeding 160° F. (71° C.), which cancause scalding when the swimming pool heater cycles on again, and thewater is permitted to return directly into the swimming pool.

Yet another reason to remove water from the solar collector when it isnot in use is to reduce stress on the collector's mounting structuresand hardware. The weight per square foot of a solar collector is doubledwhen it is full of water. Evacuating water from the solar collector canthus increase the service life of the collector, its mounting structuresand hardware.

One solution to the problem of stagnant pool water is to simply drainthe solar collectors and associated piping to waste each time the solarpool heater is turned off. This solution is unsatisfactory because newmake-up water would continually be required, which is expensive,wasteful and would require additional heating. U.S. Pat. No. 4,044,754discloses an automated freeze protection system in which a temperaturessensor automatically actuates appropriate valve means to rapidly drainwater from a solar collector when temperature within the collectorapproaches 32° F. (0° C.). U.S. Pat. No. 4,280,478 discloses a freezeprotection apparatus for solar collectors in which the working fluidcontained in the solar collector is permitted to drain from both theinput and output tubes of the collector when a first predeterminedtemperature of the working fluid is detected. The collector filledthrough both the input and output tubes when a second predeterminedtemperature is detected.

Another solution would be to drain the solar collector into the fillline, or surge tank if available, each time the solar pool heater isturned off. U.S. Pat. No. 4,237,862 discloses a closed, pressurizedsolar heating system utilizing a valveless gravity drain into a sumptank.

A third option, if the pool heating apparatus is located sufficientlyclose to the pool, is to run a gravity drain line across the pooldecking to the surface of the pool. However, the gravity drain linewould present a safety hazard.

BRIEF SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a method for positiveevacuation of water from a solar collector, comprising

-   -   i) pumping water from a swimming pool through a feed line to a        solar collector and back through a return line to said swimming        pool during operation of said solar collector;    -   ii) diverting a portion of pumped water from said feed line so        that it bypasses said solar collector and is returned to an        inlet of a water pump during operation of said solar collector,        thereby creating a bypass flow from said feed line to said water        pump;    -   iii) terminating operation of said solar collector by closing a        water inlet to said feed line; and    -   iv) positively evacuating water from said solar collector using        suction created by said water pump and said bypass flow until        substantially all water has been removed from said solar        collector.

In another aspect, the present invention relates to a system forpositive evacuation of a solar pool heating apparatus, comprising

-   -   a) a water feed line having an inlet and an outlet, and adapted        to convey water from a swimming pool to a solar heating        apparatus,    -   b) an inlet valve to open and close said inlet of said water        feed line,    -   c) solar heater control means for opening and closing said inlet        valve in response to data received from at least one of a water        temperature sensor and a solar energy sensor,    -   d) a return line having an inlet and an outlet, and adapted to        convey water from said solar heating apparatus back to said        swimming pool,    -   e) a solar heating apparatus comprising an intake manifold        operatively connected to said outlet of said water feed line and        a solar collector panel, and an exhaust manifold operatively        connected to said inlet of said return line and said solar        panel,    -   f) a bypass line connecting said water feed line and said return        line, said bypass line adapted to convey water from said water        feed line and said return line to an inlet of a filtration pump        of said swimming pool,    -   g) a bypass valve located in said bypass line,    -   h) a water level sensor to indicate whether water is present in        said water feed line, said water level sensor being located        downstream of said bypass line,    -   i) bypass valve control means to close and open said bypass        valve in response to data received from said water level sensor,

such that a portion of water flowing towards said solar heater apparatusis permitted to flow through said bypass line when said water levelsensor indicates water is present in said water feed line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one embodiment of a system whichcan be used to positively evacuate a swimming pool solar heatingapparatus according to the invention.

FIG. 2 is a circuit diagram of relay switch for controlling operation ofa three way valve to govern the diversion of water into a solar heatingcollector from a pool water filtration system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:

The inventor has discovered stagnant water may be positively evacuatedfrom a solar collector and its associated piping through the use of abypass line which creates a suction effect in combination with the pumpof the pool filtration system. When the solar water heating circuit isturned off, suction created by the filtration pump rapidly evacuates allor substantially all water present in the solar collector. Thus,“positive evacuation of a solar collector” means gravity drainage aidedby the filtration pump's suction.

In order to achieve positive evacuation of water from the solarcollector, the system should include a water level switch on the feedline to the solar collector, a drain valve that allows the pool water toevacuate from the solar collector and associated piping when water ispresent, a control mechanism that relays information from the waterlevel switch to the drain valve, a small drain line that connects thesolar pool heater feed and return lines to pump inlet, and a check valveto prevent by-pass.

The invention will be further described by reference to a preferredembodiment illustrated in the attached drawings.

FIG. 1 illustrates the operation of the inventive method as applied to acommercial swimming pool equipped with a solar heating apparatusincorporated into a conventional continuous filtration system. When thesolar heater is not being used, water from swimming pool 10 is piped toa pump 20 which forces the water through filter 30, water temperaturesensor 35, check valve 40 and three-way valve 50 before being returnedto swimming pool 10 via return line 55.

Pump 20 is operated continuously, and thus water is continuouslyfiltered, in accordance with public health codes. Accordingly, waterreturning from return line 90 cannot gravity drain through the outlettee 100 due to the pressure in the main filtration line generated bypump 20.

Three-way valve 50 is preferably a motorized ball valve. Electronictemperature control 60 opens and closes three-way valve 50 in responseto data received from water temperature sensor 35 and solar sensor 65.During solar heating operation, three-way valve 50 is open and a portionof the filtered water is piped through water feed line 70 past T-joint71 and water level sensor 4 to solar collector 80.

As illustrated in FIG. 1, the water is typically piped into a lowerintake manifold of solar collector 80, and then rises through aplurality of small conduits before being collected in an upper exhaustmanifold. Thermal energy absorbed by the solar collector from sunlightis transferred to the water as it rises in the collector's conduits.Water thus heated in solar collector 80 is piped through return line 90past T-joint 82, isolation ball valve 98, check valve 95 and T-joint 100into return line 55, which delivers the heated water to pool 10.

A positive evacuation flow is created by installing a bypass line 72between water feed line 70 and return line 90, and draining bypass line72 to a return line 76 which feeds this water to pump 20. Duringoperation of the solar heater, relay control switch 3 maintains drainvalve 78 in the open position while water level sensor 4 indicates wateris present. A small amount of water is thus permitted to flow from waterfeed line 70 through T-joint 71 into bypass line 72 and through T-joint74 into return line 76, and then past drain valve 78 and back to pump20. Alternatively, T-joint 74 and drain valve 78 may be combined intoone three-way valve that performs the functions of both components.

In similar fashion, a small amount of heated water returning to the poolthrough return line 90 is permitted to pass through T-joint 82 intobypass line 72. This heated water then flows past check valve 84 toT-joint 74 and into return line 76, which may be operatively connectedto the pump inlet line, for example by a T-joint or a saddle fitting.The water in return line 76 is thus drawn by pump 20, thereby creating apositive evacuation flow.

Electronic temperature control 60 closes three-way valve 50 either whenwater temperature sensor 35 indicates the pool water is at or above thedesired temperature or when solar sensor 65 indicates usable solarenergy required for heating the pool is no longer available. Closingthree-way valve 50 closes the flow path to solar collector 80 and mayalso turn off a solar booster pump, if it is present as part of thesystem. Pump 20 continues to draw water from return line 76.Accordingly, pool water present in water feed line 70, solar collector80 and return line 90 is positively evacuated through open drain valve78 by pump 20.

A vacuum relief valve 00 may be employed to allow air to enter solarcollector 80, water feed line 70 and return line 90 to aid in waterevacuation. Vacuum relief valve 00 may be placed in the outlet header ofsolar collector 80 opposite the end that return line 90 exits solarcollector 80. Alternatively, vacuum relief valve 00 can be placed inwater feed line 70 above water level sensor 4 or in return line 90 aboveT-joint 82.

Relay control switch 3 closes drain valve 78 when water level sensor 4indicates water is no longer present, i.e., that the water has beenevacuated to the level of water level sensor 4. Closing drain valve 78prevents air from being introduced to pump 20, which could causecavitation, loss of prime and pump function.

Water level sensor 4 is preferably located within the building, and thuswithin a heated air space. Locating water level sensor 4 in this heatedair space will ensure the portions of water feed line 70 and return line90 which extend outside the building and which are thus exposed to theelements are completely evacuated before drain valve 78 is closed.

Once solar collector 80 and the exposed portions of water feed line 70and return line 90 have been evacuated, there is no danger of stagnantpool water freezing or scalding water being released into the pool.Moreover, the weight of the collector and its associated piping has beensignificantly reduced, thereby extending the service life of thesecomponents.

The solar pool heater will cycle on when water temperature sensor 35indicates the pool water temperature has fallen below the desiredtemperature and solar sensor 65 indicates usable solar energy requiredfor heating the pool is available. Electronic temperature control 60will then open three way valve 50, thereby permitting water to flowthrough water feed line 70 towards solar collector 80. Relay box 3 opensdrain valve 78 once water level sensor 4 reports the presence of water,thereby allowing a small amount of pool water to once again bypass thesolar collector 80 to create a positive evacuation flow.

It should be noted that when three way valve 50 diverts water towardssolar collector 80 air present in the system will be purged by the forceof water flow through return line 50 into pool 10.

The various valves, pumps, piping and filter comprising the system ofthe present invention are conventional and well known to those ofordinary skill in the art. Thus, for example, drain valve 78 ispreferably a motorized ball valve, commercially available from HaywardIndustrial Products Inc., Elizabeth, N.J., under Hayward Series EAAutomated Ball Valve, Model No. EATB1075STE. However, a solenoid valvemay also be used in place of a motorized ball valve for drain valve 78.

FIG. 2 illustrates one embodiment of a wiring diagram to controloperation of drain valve 78. As illustrated therein, water level sensor4 may be a conventional float valve, powered with conventional 120 voltpower, with its “up” position designated as the open position. Asuitable single stage liquid level switch is commercially available fromOil-Rite Corporation, Manitowoc, Wis., under model No. B-2364-1.

Output from water level sensor 4 is operatively connected to relaycontrol switch 3, which is also powered using conventional 120 voltpower. A suitable single stage relay control switch is commerciallyavailable from Oil-Rite Corporation, under model No. A-4621-1. Outputfrom the relay control switch is operatively connected to drain valve78.

The above-described method and system provide a fail-safe drainagecontrol should filtration pump 20 ever lose power while the solarcollector is operating and filled with water. Should pump 20 fail, waterpresent in water feed line 70, solar collector 80, return line 90,bypass line 72 and return line 76 will drain by gravity to pool 10 viathe inlet line through pump 20 and return line 55.

Those of ordinary skill in the art will recognize many variations of theabove system may be made without departing from the scope and spirit ofthe basic invention. For example, a conventional gas-fired heater may beincorporated into the system using a conventional by-pass valve.Similarly, the system may be fitted with at least one pressure reliefvalve and/or at least one vacuum relief valve. While the invention hasbeen illustrated by reference to a commercial swimming pool (whichrequires continuous filtration), the invention is equally applicable toa residential pool.

1. A method for positive evacuation of water from a solar collector,comprising i) pumping water from a swimming pool through a feed line toa solar collector and back through a return line to said swimming poolduring operation of said solar collector; ii) diverting a portion ofpumped water from said feed line so that it bypasses said solarcollector and is returned to an inlet of a water pump during operationof said solar collector, thereby creating a bypass flow from said feedline to said water pump; iii) terminating operation of said solarcollector by closing a water inlet to said feed liner; and iv)positively evacuating water from said solar collector using suctioncreated by said water pump and said bypass flow until substantially allwater has been removed from said solar collector.
 2. The method of claim1, wherein a water level sensor located in said feed line is used todetermine when substantially all water has been removed from said solarcollector.
 3. The method of claim 1, further comprising diverting aportion of water exiting from said solar collector via said return lineto said swimming pool is diverted from said return line and added tosaid bypass flow.
 4. A system for positive evacuation of a solar poolheating apparatus, comprising a) a water feed line having an inlet andan outlet, and adapted to convey water from a swimming pool to a solarheating apparatus, b) an inlet valve to open and close said inlet ofsaid water feed line, c) solar heater control means for opening andclosing said inlet valve in response to data received from at least oneof a water temperature sensor and a solar energy sensor, d) a returnline having an inlet and an outlet, and adapted to convey water fromsaid solar heating apparatus back to said swimming pool, e) a solarheating apparatus comprising an intake manifold operatively connected tosaid outlet of said water feed line and a solar collector panel, and anexhaust manifold operatively connected to said inlet of said return lineand said solar panel, f) a bypass line connecting said water feed lineand said return line, said bypass line adapted to convey water from saidwater feed line and said return line to an inlet of a filtration pump ofsaid swimming pool, g) a bypass valve located in said bypass line, h) awater level sensor to indicate whether water is present in said waterfeed line, said water level sensor being located downstream of saidbypass line, i) bypass valve control means to close and open said bypassvalve in response to data received from said water level sensor, suchthat a portion of water flowing towards said solar heater apparatus ispermitted to flow through said bypass line when said water level sensorindicates water is present in said water feed line.
 5. The system ofclaim 4, wherein said filtration pump is capable of filtering a minimumamount of water equal to four times a volume of said swimming poolwithin a 24 hour period.
 6. The system of claim 4, wherein said inletvalve of said water feed line comprises a three-way motorized ballvalve.
 7. The system of claim 4, wherein said inlet valve of said waterfeed line comprises a two-way valve in combination with a booster pump.8. The system of claim 4, further comprising a gas-fired pool heater. 9.The system of claim 4, further comprising at least one pressure releasevalve.
 10. The system of claim 4, further comprising at least one vacuumrelief valve.